/*
 * Copyright 2010 eBusinessInformation
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package com.excilys.blog.refactoring.refactored;

import com.excilys.blog.refactoring.GeoPoint;

abstract class PositionDelta {
    protected final double latitudeDelta;
    protected final double longitudeDelta;

    public PositionDelta(GeoPoint firstPoint, GeoPoint secondPoint) {
        latitudeDelta = secondPoint.getLatitudeDelta(firstPoint);
        longitudeDelta = secondPoint.getLongitudeDelta(firstPoint);
    }

    public boolean isBetterCandidate(PositionDelta delta) {
        return isInGoodDirection() && hasSharperSlope(delta);
    }

    protected abstract boolean isInGoodDirection();

    private boolean hasSharperSlope(PositionDelta delta) {

        if (delta == null) {
            return true;
        }

        double crossMultiplication = crossMultiply(delta);

        return crossMultiplication < 0;
    }

    private double crossMultiply(PositionDelta delta) {
        return latitudeDelta * delta.longitudeDelta - delta.latitudeDelta * longitudeDelta;
    }

}